Optical ferrules are used in connecting the ends of optical fibers. The ferrule has the shape of a tiny tube with a canonical entry into which the fiber end is inserted as a means of providing optical connection between fibers. In this way, vast lengths of fibers can be connected with a minimum of degradation at the points of connection.
Their small size, about 1/2 inch long and about 1/16 inch in diameter, and requirement of high precision make current ceramic optical ferrules fairly expensive. Ceramic optical ferrules are usually made by injection molding or extruding alumina or other suitable ceramic material. These methods are very expensive, but they have been necessary to produce the ferrules which must have a very precise inner diameter.
Electrophoresis is a process whereby particles in a liquid suspension are drawn toward an electrode when an electric field is applied across the suspension. The direction and rate that a particle travels depends on the charge present on the particle's surface, the conditions of the medium in which the particle is suspended, conditions at the electrode(s), the electrical potential applied and the characteristics of the particle itself.
Often, the surface charge on a particle can be varied by changes in the pH, the concentration of electrolyte in the medium or by addition of a polyelectrolyte adapted to interact with the particle surface.
In the past, electrophoresis has been used to produce alumina coatings on stainless steel plates by Choudhary et al., Trans. J. Br. Ceram. Soc. 81, pp. 189-193 (1982). Choudhary et al. employed an aqueous suspension containing the alumina particles.
Electrophoresis has also been used to deposit enamel coatings from various suspensions onto workpieces. An example of enamel deposition is disclosed in U.S. Pat. No. 4,466,871 to Kaup et al.
Some have used electrophoresis to produce three-dimensional ceramic shapes such as described by Heavens in the article "Manufacture of Beta Alumina Shapes by Electrophoretic Deposition," Brit. Ceram. Proc., No. 38, Davidge, R. W. ed., pp. 119-126 (1986). Most of the three-dimensional shapes formed have been deposited on relatively large diameter electrodes (e.g., greater than 1 inch wide). Most of these prior art processes have involved the use of organic suspension media as opposed to aqueous media. Aqueous systems can have problems caused by hydrogen evolution at the cathode or oxygen evolution at the anode due to electrolysis of water.
There remains a need for an inexpensive process for reliably producing ceramic parts having very small inner diameters in proportion to the part thickness and close dimensional tolerances.